ELECTRON INTERSUBBAND SCATTERING BY CONFINED AND LOCALIZED PHONONS IN REAL QUANTUM WIRES

The present study deals with electron intersubband scattering in real quantum wire structures. Both the multi-subband structure and confined phonon modes are considered together. The rates of scattering by confined longitudinal-optical (LO) phonons and by surface-optical (SO) phonons are calculated taking into account all possible LO phonon modes as well as all possible electron intersubband transitions. The estimations of transition rates for GaAs/AlAs QWIs have shown that intrasubband electron scattering and most intersubband transitions are due primarily to scattering by confined LO phonons, but in resonant intersubband transitions the contribution of SO phonons may be dominant when the phonon energy is close to the intersubband energy separation. Moreover, electron-SO-phonon scattering might play an important part in low-temperature electron transport because the GaAs-like so mode is shifted towards lower frequencies compared with that of LO phonons. The energy dependence of the total scattering rate in an ideal quantum wire exhibits multiple sharp peaks related to each intersubband transition. These peaks originate from the resonant nature of the density of states in ideal one-dimensional systems. It is demonstrated that in real quantum wires with variable thickness the resonant peaks broaden or even disappear due to variation of subband energies.